Attempt to lock this reader/writer lock for read. Return 0 on success, and a non‐zero value if the lock is currently locked for write or if there are writers waiting for this lock. If successful, unlock must be used to release this lock.
Attempt to lock this reader/writer lock for read. Return 0 on success, and a non‐zero value if the lock is currently locked for write or if there are writers waiting for this lock. If successful, unlock must be used to release this lock.